The present disclosure relates to a vertical microelectronic component and to a corresponding production method.
The HEMT transistor (high electron mobility transistor) is a particular configuration of the field-effect transistor, which is suitable in particular for use at high frequencies owing to the very small component capacitances. In terms of structure, the HEMT transistor consists of layers of various semiconductor materials with band gaps of different sizes (so-called heterostructure), for which the material system GaN/AlGaN is for example used. If these two materials are deposited on one another, a two-dimensional electron gas which can be used as a conductive channel, since the electron mobility therein is very high, is formed at the interface of these materials on both sides of the GaN.
Conventional HEMT transistors with the material system GaN/AlGaN are produced by epitaxial deposition of GaN/AlGaN heterostructures on planar or, alternatively, prestructured substrates in a continuous layer. It is possible to deposit both high epitaxial layers on monocrystalline GaN substrates and heteroepitaxial layers on sapphire, silicon carbide or silicon substrates. The most economical variant in this case is provided, in particular, by the possibility of being able to use large substrates, for example by selecting silicon.
Corresponding production methods are known for example from US 2011/0101370 A1, US 2006/0099781 A1 or U.S. Pat. No. 6,818,061 B2.
In such GaN/AlGaN heterostructures, the electron mobilities are typically more than 2000 cm2/Vs and the charge carrier densities are more than 1013 cm−2 in the channel region. These properties offer the potential of producing power transistors with extremely low conduction losses. However, these advantageous properties can be used for the aforementioned layer structure GaN/AlGaN on silicon wafers only by lateral components, which generally entails a larger area requirement in comparison with known vertical power transistors on silicon or silicon carbide. This problem is particularly relevant for high voltage classes above 600 V since, in the case of lateral components, a high voltage strength is possible only by increasing the distance between the gate and drain terminals. The performance advantages of GaN/AlGaN components over those made of silicon or silicon carbide can therefore sometimes be overcompensated for by the greater surface area used.